The present invention relates to a method for making bisphenol monochloroformate polycarbonate oligomers useful for making high molecular weight aromatic polycarbonates and cyclic oligomeric carbonates.
Prior to the present invention, as shown by Miller et al, U.S. Pat. No. 3,193,528, bisphenol monochloroformate monomers were prepared by reacting phosgene with a dihydroxy aromatic compound in the presence of dilute aqueous caustic. The resulting bisphenol monochloroformate monomers can be subsequently polymerized, or copolymerized by dissolving the bisphenol monochloroformate monomers, or a mixture of monochloroformates of different dihydroxy aromatic compounds in an organic solvent in the presence of aqueous caustic and a polymerization catalyst. Additional procedures for making, or using monochloroformate monomers are shown by U.S. Pat. No. 3,254,051.